Apparatus for metal plating



Aug. 9, 1932. K. c. MONROE APPARATUS FOR METAL PLATI-NG Filed March 29,1929 Patented Aug. .9, 1932 UNITED STATES PATENT OFFICE KENNETH C.MONROE, F BRIDGEPORT, CONNECTICUT, ASSIGNOR TO BRIDGEPORT BRASS COMPANY,OF BBIDGEPORT, CONNECTICUT APPARATUS FOR METAL PLATIN G Applicationfiled March 29, 1929. Serial No. 350,994.

This invention relates to apparatus for metal plating, and moreparticularly for the electro-deposition of such metals as chromium orthe like, from the solutions of their salts or acids.

The electrodeposition of chromium, for example, has been carried on forsome time from chromic acid baths, and while it has been determined thata satisfactory and lasting deposit may be formed in this manner, it haslikewise been determined that satisfactory results are more frequentlyobtained when careful control is exercised in the composition of thesolution, the temperature of the bath and the voltage between the anodeand the cathode. I contemplate bythis invention, a method and apparatuswhereby a more exact control may be exercised over the current voltagewithin the solution or between the anode and cathode.

It will be appreciated that when chromium or other metal plating iscarried on commercially relatively large tanks are used to contain thesolution. In the usual form where the current enters the bus bars, orthe current carrying members suspended over the tank, at one end of thetank, the amount of metal in the circuit is considerably varieddepending upon the position in the tank ofthe articles to be plated. Thesame is true even if the current enters the bars at one end of the tankand leavesat the other end, if the cross section of these bars is notproperly determined. It will, of course, be obvious that if there ismore metal in the circuit at some times than at others, there 'will be agreater voltage drop within the line, and hence a smaller voltage dropwithin the solution or between the anode and cathode, even though thevoltage of the supply of current is maintained at a constant value.

By the present invention, I contemplate so arranging the anode andcathode bars that regardless of the point in the tank at which thearticles are suspended, there will be the Another object of theinvention is the provision of an apparatus for metal plating, such thatthe voltage drop between the racks upon which the work is hung may bekept constant.

To these and other ends, the invention consists in the novel featuresand combinations of parts to be hereinafter described and claimed.

In the accompanying drawing:

Fig. 1 is a top plan view, partly in diagrammatic form, of an apparatusfor the electrodeposition of metal;

Fig. 2 is an end view of the electroplating tank and the leads from thesource of current;

Fig. 3 is a sectional view through the tank on line 33 of Fig. 1.

To illustrate a preferred embodiment of my invention, I have shown in adiagrammatic way, a direct current generator at 10, having lead wires 11and 12, carrying the current to the anode and cathode bars 13 and 14. Avoltage regulator 15 is placed across the service lines 11 and 12, andis preferably connected thereto as near as possible to the tank itself,so as to maintain, as nearly as possible, a constant voltage passing tothe bus-bars 13 and 14 across the tank.

As shown in the drawing, I employ three of the anode bars 13 and two ofthe cathode bars 14, although this number may, of course, be varied asconditions may require. Each of these bars is connected with the properservice line 11 or 12, by means of relatively thin wide conductors 16,which pass around the anode and the cathode bars 13 and 14, and afterrising perpendicularly to the proper height are carried horizontally asat 17 to have their ends embrace relatively heavy conductors 18, whichin turn are oined fiatwise together to comprise the leads 11 and 12.These thin wide conducting strips 16 and 17 are sufiiciently flexible topermit the shifting of the anode and cathode bars towork 21 to beplated, and likewise, to make good contact with the racks which carrythe anodes 22. These bars are preferably of copper although any goodconducting metal may be used, and I prefer to use lead for the anodes22.. It will also be noted that the risers 16 are connected to the anodebars adj acent one end of the tank, and to the cathode bars adjacent theopposite end of the tank.

As previously stated, I employ in the form of my invention shown in thedrawing, three anode bars and two cathode bars. It will be apparent thatif these bars were allof the same size and the work were suspendedadjacent one end of the tank, for instance adjacent the left-hand'end,as shown in Fig. 1, a relatively great length of the anode bars would beemployed in the circuit and a relatively short length of the cathodebars, while the reverse would be true if the work were suspended at theother end of the tank. As there are a greater number of vanode-bars thiswould result in there being more metal employed in the circuit when agreater length of the anode bars are used (provided, of course, that thebars were of the same size in cross section), and, therefore, thevoltage drop between the anode and cathode in one case would be lessthan in the other.

To overcome this variation and to provide for a constant voltage betweenthe anodes and cathodes, regardless of where the Work is hung, 1 sodetermine the cross sectional size of the anode and cathode bars thatthe sum of the cross sectional area of the anodes will be equal to thesum of the cross sectional area of the cathodes. For instance, in thepresent case where three anode and two cathode bars are employed, thecross section of each anode bar is two-thirds thecross section of acath-.

ode bar. By having one more anode bar than cathode bars I am able tohave an anode bar on each side of each cathode bar, and thus secure moreuniform results and more 'even distribution of the chemical action whichtakes place.

While I do not wish to be limited to exact dimensions, for the purposeof fully illustrating my invention I have obtained very satisfactoryresults from using anode bars of rectangular shape in cross section andone and one-half inches wide and two inches thick, and using cathodebars one and onehalf inches wide and three inches thick. I may alsocarry out this principle through the rest of the circuit by employingfor the risers 16, and horizontal portions 17, which lead from the anodebars, copper strips six inches wide and one-quarter inch in thickness,while therisers 16 and horizontal extensions 17 leading from the cathodebars may be six inches wide and three-eighths inch thick. In likemanner, the conductors 18 from the anode bars may be-six inches wide andonehalf inch in thickness, while the members 18 sults in theelectrodeposition of metals, such i as chromium, for example, it will beapparent that improved results will be obtained by the use of myimproved method and apparatus;

While I have shown and described a pre- -ferred embodiment of myinvention, it is to be understood that the same is not to be limited tothe exact details shown and described, but is capable of modificationand variation within the spirit of the invention and within the scope ofthe appended claims.

What I claim is:

1. Apparatus for the electrodeposition of metal from solution,comprising a source of current, a container for the solution, anode andcathode bars supported adjacent the container which in-turn support theanodes and the work, means to conduct current from the source to saidbars, the cross sectional area of the anode bars being substantiallyequalto that oi the cathode bars, and the ends of said anode barsconnected to the source of current belng remote from the ends of thecathode bars connected to the source of current, the number of anodebars being unequal to thatof the cathode bars, and said bars beingalternately placed.

2. Apparatus for the electrodepositiom of metal from solution,comprising a container for the solution, anode and cathode barssupported above the container with a cathode bar between each twoadjacent anode bars, a source of current, conductors leading from saidsource to one end of the anode bars, conductors leading from said sourcetothe re mote ends of the cathode bars, said bars being disposed inoverlapping relation, the number of anode bars being greater than thatof the cathode bars and the aggregate conductivity of the anode barsbeing equal to that of the cathode bars.

3. Apparatus for the electrodeposition of metal from solution,comprising a series of anode bars and a series of an unequal number ofcathode bars arranged in overlapping relation with a cathode bar betweeneach two adjacent anode bars, a source of current connected to theadjacent ends of the anode bars and connected to the ends of the cathodebars remote from the anode connection, and'the aggregate cross-sectionalarea of the anode bars being substantially equal to the aggregate crosssectional area of the cathode bars.

' tainer, and connections from said members I 4; Apparatus for'electrodeposition of metal from solution, comprising a container forthe solution, anode and cathode bars supported in, parallel relationabove the container, a source of current, connections from said sourceof current to the anode and cathode bars, said connections includingleads from the source of current and relatively wide, thin, flexibleconducting strips connected to the anode and cathode. bars and extendingupwardly to said leads whereby the positions of the anode andcathode-bars may be laterally adjusted relatively to the container byflexing said conducting stri s.

5. Apparatus for -electrodliposition of metal from solution, comprisinga container for the solution, an anode circuit comprising anode memberssupported adjacent the conto a source of current, a cathode circuitcomprising cathode members adjacent the con tainer, and connections fromsaid members to the source of current, said connections being at one endof the anode bars and at the opposite end of the cathode bars, saidanode connections having a conductivity equal to that-

